The present invention relates to an encapsulating machine and particularly to an improved machine employing a pair of offset die rolls for, in one embodiment, encapsulating medicinal tablets with a plastic film material, such as gelatin.
As used herein, the term “tablet” refers to a preformed shape, such as a round tablet or an elongated tablet frequently referred to as a caplet. When a medicament, such tablets are preformed in conventional tabletting presses and typically include excipients and fillers in addition to the active ingredients. Encapsulating such tablets with plastic films, such as gelatin, has been well known since the early 1950's, as disclosed in U.S. Pat. No. 2,775,081 showing equipment employing two offset die rolls, one of which transports tablets positioned on a gelatin film into the nip between the die rolls for encapsulation of the tablets by a second gelatin film on the other of the die rolls. In order to adjust the pressure between the die rolls for proper sealing of the film around the tablets, one of the die roll drive shafts has bearings mounted in elongated slots which bearings are urged by a pin and spring mechanism to provide an adjustable pressure between the die rolls.
Although such a system provides a basic adjustment mechanism for pressure between co-acting dies in a tablet encapsulating machine, it does not easily accommodate for changes due to wear of the die rolls during use of the machine nor does it accommodate dynamic lateral adjustability of one die roll to the other.
More current tablet encapsulating machines are disclosed in, for example, U.S. Pat. No. 6,209,296, which includes direct gear-driven die rolls and tablet feeding mechanism to synchronize the depositing of tablets on one gelatin film prior to introduction into the nip between two die rolls. Although such a system provides clocked and synchronized depositing of tablets onto a gelatin film, the use of direct gear-driven die rolls and the tablet feeding mechanism will, during use, cause wear and backlash between the numerous gears employed. Such a system is not easily adjustable to allow resynchronization of the introduction of tablets into the die rolls upon wear of the gears.
Also, tablet encapsulating machines employ rolls, known as mangle rolls, to grab and remove the webs of encapsulating film from the die rolls once the encapsulated tablets have been remove from the films which are, at this time, laminated to one another. On occasion, the mangle rolls become jammed with the web material necessitating stopping of the entire machine while the jam is cleared. This leads to undesirable down time during a production run. There exists a need, therefore, for an improved web take-up system which is less prone to jamming and, if jammed, can be easily and quickly cleared.
Further, with existing die rolls, some difficulties have been encountered forming a tight peripheral seal of the gelatin film on preforms as well as wear on the die rolls during use.
Thus, there remains a need for a tablet encapsulating machine of the type which deposits tablets on a gelatin film in advanced of the nip between die rolls having cavities for encapsulating tablets with plastic film material, such as gelatin, around the tablets, and which can accommodate continued use of the machine, including the wear of the co-acting dies themselves. There also exists a need for an encapsulating machine which easily accommodates adjustment for synchronizing the clocked positioning of tablets on one sheet of plastic film on a die roller, including precise positioning with respect to the tablet die cavity therein and one which efficiently seals the preform tablets and subsequently removes the web material from the die rolls.